Getting your period is a rite of passage for young girls, but there’s a lot for them to figure out too — from dealing with painful cramps and PMS to learning how to use all the different types of menstrual products. Tampons and menstrual cups can be tricky to use at first, and pads are notoriously bulky and uncomfortable. And, of course, the fear of leaks is a constant worry. That’s where Kt. By Knix comes in.
Made specifically for teens, the brand’s line of period underwear and swimwear is designed to absorb menstrual flow so that girls can feel more comfortable and confident during their period. And Kt. By Knix’s new activewear collection, which just launched in March, means that teens now have a plethora of period protection options whether they plan on working out or just hanging out.
What is Kt. By Knix?
Kt. By Knix is the “little sister brand” to the period apparel company Knix. A top performer in the Good Housekeeping Institute Textiles Lab evaluations and a favorite among consumer testers, Knix makes our best overall period underwear and our best overall period swimwear. Kt. By Knix underwear and swimwear has also performed well in our Lab tests, so we were excited to see that the brand was broadening its Leakproof collection by adding period activewear that includes everything from leggings, tanks and shorts to super cute sport dresses and tennis skorts.
The main difference between the two brands is that Kt. By Knix is sized to appropriately fit the bodies of teens and tweens. Because our experts say it’s important to get the just-right fit with period underwear and swimwear in order to prevent leaks, it’s a good idea to check Kt. By Knix's size chart, which includes a list of measurements as well as the equivalents of both kids’ and adults’ sizes to take out any guesswork. The brand offers an impressively wide range of sizes from XXS (which fits kids’ pant size 7) to XXL (which fits adults’ pant sizes 20–22) so there are options for nearly everyone.
And while the initial cost may seem pricey in comparison to regular underwear, swimwear and activewear, Kt. By Knix saves on the cost of disposable menstrual products since the garments are washable and reusable (so more sustainable too!).
How do Kt. By Knix's period products work?
Kt. By Knix’s patented leakproof technology features three layers built into the gusset of the underwear, swimwear and activewear so the wearer stays dry and comfortable: The first layer is designed to wick away sweat and moisture; the second layer absorbs menstrual flow; and the third outer layer helps prevent leaks. While Kt. By Knix feels slightly thicker than regular underwear, each layer is thin and the design is seamless so it doesn’t look or feel bulky. And, it’s nowhere near as noticeable as wearing a pad.
Each garment comes in different absorbencies, so make sure to select the right product for the level of flow. Super absorbs the amount of five and a half super tampons' worth; heavy holds about three super tampons’ worth, while moderate absorbs about two and half super tampons and light holds the same as one regular tampon.
Each item can be worn on its own, but each can also be used as backup on heavier days along with a tampon or menstrual cup to minimize the chance of leaks.
Our favorite Kt. By Knix styles
Absorbency: Moderate (about 2.5 super tampons’ worth) | Sizes: XXS–XXL | Materials: Nylon, Lycra, cotton, carbon, polyester, polyurethane | Colors: 8
We love Kt. By Knix’s Leakproof UltraThin No-Show Underwear because it offers discreet protection for medium-flow days under body-hugging pants and leggings. Online reviewers describe the stylish seamless design of the bikini as “comfortable” and “good quality.” One said, “I have two girls that play sports and these are perfect for them. They don’t complain of any discomfort and the best part… they wash very well! Highly recommend this product.”
Absorbency: Moderate (about 2 super tampons’ worth) | Sizes: XXS–XL | Materials: Nylon, spandex, polyurethane film | Colors: 5
No more sitting on the sideline during beach and pool days. Wearing this fully lined one-piece constructed with a hidden layer that absorbs up to two tampons' worth, your teen can dive in whenever they want. Our experts appreciate the secure racerback straps that stay securely in place during laps. The simple and sleek silhouette comes in the bold graphic print pictured here as well as a red floral, black and two different shades of blue.
Many online reviewers who bought the swimsuit for their daughters gave it five stars, with one saying it “gave my daughter the confidence to swim with her first period and allowed her to have fun and be a kid without any worries!” Still, some wished it covered more in the rear (the brand says the bum coverage is "medium").
Absorbency: Super (about 5.5 super tampons’ worth) | Sizes: XXS–XXL | Materials: Nylon, spandex, modal, seaweed, polyester, polyurethane film | Colors: 8
For overnights, the Sleepover Short designed for nighttime wear is the way to go. This one is Kt. By Knix’s most absorbent underwear, holding up to five and a half super tampon’s worth. The brand says the longer gusset helps prevent leaks even when shifting positions. One reviewer said of her daughter’s pair, “The padding goes high in the back. They are tight enough that when she turns during her sleep, it doesn’t move.” Another noted, “I can bleed through a regular pad in less than an hour. These are great for overnight, during the day, and everything else.” However, one person reported size discrepancies among the colors.
Absorbency: Moderate (about 2 super tampons’ worth) | Sizes: XXS–XXL | Materials: Nylon, Lycra, cotton, carbon, polyester, elastane, polyurethane film | Colors: 2
Playing sports, working out or, let’s be honest, doing just about anything while wearing a thick pad can be extremely uncomfortable — not to mention that it can be hard to hide under tight-fitting clothes. That’s why Kt. By Knix’s new Leakproof Active Legging is such a game-changer. The stretchy, seamless fabric is designed with a built-in liner that won’t show for a streamlined look and feel so your kid can feel confident whatever they’re doing.
How do you wash Kt. By Knix period products?
What makes Kt. By Knix so convenient is that everything in its line, from the period underwear to the swimsuits and activewear, is machine washable in cold water, which means one less thing to worry about. To ensure your garment lasts long term, follow the care instructions listed on the item’s label or website description, because some products may have slightly different guidelines when it comes to drying. For instance, the brand recommends laying the Leakproof Active Legging flat to dry, while the Super Leakproof Sleepover Short can be tumble dried on low. Bleach, ironing and dry cleaning should all be avoided.
Our experts offer this tip: Rinse your period underwear, swimwear or activewear in the sink or shower before laundering to prevent staining other clothes in the washing machine.
The bottom line: Is Kt. By Knix worth buying?
Yes. Both Knix and Kt. By Knix period underwear and swimsuits have proven to be effective at absorbing liquid in our Textiles Lab tests and they are also favorites of our consumer testers. Based on how the rest of the brand’s product line has performed, we feel good about recommending Kt. By Knix’s new activewear collection even though we have yet to test them in the Lab.
Yolanda Wikiel is a freelance writer and editor based in New Jersey, where she lives with her husband, overly energetic toddler and supremely lazy calico. She has covered everything from home, food, and life skills to fashion, travel, and consumer goods for over a decade. Her work has appeared in Parents, Real Simple, Good Housekeeping, Oprah and Woman’s Day.
